1. Field of the Invention
The present invention relates to a connection structure formed between two electronic components such as a liquid-crystal panel and a film connector.
2. Description of the Related Art
A film connector such as the one depicted in FIGS. 4A and 4B (where FIG. 4A is a fragmentary cutaway plane view, and FIG. 4B is a cross section along Yxe2x80x94Y in FIG. 4A) may be used to electrically connect the connection terminals of a liquid-crystal panel with the connection terminals on a motherboard. This film connector is configured such that conductor layers 42 in the form of patterned copper foil are formed on a film substrate 41 composed of polyester or another flexible resin, and a cover film 43 is laid over the conductor layers 42. In this structure, the cover film 43 is configured such that the conductor layers 42 remain exposed at the two ends of the flexible resin film substrate 41. Anisotropic electroconductive adhesive layers 44a and 44b are formed to the same layer thickness in the areas of the conductor layers 42 not covered by the cover film 43.
The height of the conductor layers for the connection terminals of a liquid-crystal panel is commonly 1 xcexcm or less, whereas the height of the conductor layers for the connection terminals of a motherboard is 10 to 50 xcexcm. The result is that when the connection terminals of a liquid-crystal panel and the connection terminals on a motherboard are connected using a film connector in which the anisotropic electroconductive adhesive layers at the two ends are fashioned in the same layer thickness as shown in FIG. 4B, the anisotropic electroconductive adhesive often leaks from the connections on the side of the liquid-crystal panel, creating short circuits. Another drawback is that the connections on the motherboard side acquire relatively high conduction resistance and have inadequate adhesion strength.
Such drawbacks are always present in connection structures used to connect two electronic components by means of an anisotropic electroconductive adhesive.
An object of the present invention, which is aimed at overcoming the above-described drawbacks of the related art, is to provide a connection structure obtained by connecting two electronic components by means of an anisotropic electroconductive adhesive such that the anisotropic electroconductive adhesive is prevented from leaking, and the structure is provided with connections that have low conduction resistance and adequate adhesion strength.
The inventors perfected the present invention upon discovering that the stated object can be attained by maintaining an optimum relation between factors such as the heights of conductor layers for the connection terminals of the two electronic components to be connected, the widths of the conductor layers, the width of the space between the conductor layers, and the thickness of anisotropic electroconductive adhesive layers.
Specifically, the present invention provides a connection structure comprising first electrodes on a first substrate and second electrodes on a second substrate which are electrically connected each other with an interposed anisotropic electroconductive adhesive layer, wherein this connection structure satisfies Eq. 1 below
0.5xc3x97{(A1C1+A2C2)/(B+C)}xe2x89xa6Xxe2x89xa62xc3x97{(A1C1+A2C2)/(B+C)}xe2x80x83xe2x80x83(1) 
where A1 is the height of each first electrode, B1 is the electrode width thereof, C1 is the width of the interelectrode space, A2 is the height of each second electrode, B2 is the electrode width thereof, C2 is the width of the interelectrode space (B+C=B1+C1=B2+C2), and X is the thickness of the electroconductive adhesive layer prior to connection.
The present invention also provides a connection method for electrically connecting first electrodes on a first substrate and second electrodes on a second substrate with an interposed anisotropic electroconductive adhesive layer, wherein this connection method satisfies Eq. 1 below
0.5xc3x97{(A1C+A2C2)/(B+C)}xe2x89xa6Xxe2x89xa62xc3x97{(A1C1+A2C2)/(B+C)}xe2x80x83xe2x80x83(1) 
where A1 is the height of each first electrode, B1 is the electrode width thereof, C1 is the width of the interelectrode space, A2 is the height of each second electrode, B2 is the electrode width thereof, C2 is the width of the interelectrode space (B+C=B1+C1=B2+C2), and X is the thickness of the electroconductive adhesive layer prior to connection.
The present invention also provides a film connector in which conductor layers are formed on a flexible resin film substrate, a cover film is laid over these conductor layers such that the conductor layers are exposed at the two ends of the flexible resin film substrate, and anisotropic electroconductive adhesive layers are formed in the areas of the conductor layers not covered by the cover film, wherein this film connector has a configuration in which the thickness of the anisotropic electroconductive adhesive layers, the height of the conductor layers at the two ends of the flexible resin film substrate, the width of the conductor layers, and the width of the space between the conductor layers are selected such that the electrode height of the components to be connected by means of the film connector, the electrode width, and the width of the interelectrode space satisfy the requirements of the inventive connection method.
Other objects and features of the present invention will be described or become apparent from the following disclosure.